An ADF is extensively used with a copier or similar image forming apparatus, e.g. a scanner, for automatically and sequentially feeding a plurality of documents with image thereon to an scanning position. At the scanning position, the document is illuminated to reproduce an image thereof on a media, e.g. a sheet of paper or transparency.
In the market, there are supplied two types of ADF with respect to the document path. The first type is so-called straight-path and the other type is the U-turn path. The straight-path type serves better for the documents of different thickness. After the scanning of a plurality of documents in a sequential page order, however, the order of page of the discharged document from the outlet of the ADF will be reversed compared to the original sequential order. To the contrary, while the U-turn path type ADF discharges the documents in the same sequential page order as the original document stacked in the paper cassette of the ADF, it serves better for the document of smaller thickness. That is to say, jamming of documents of thicker sheet often happens when U-turn path type ADF is employed.
Since none of the conventional ADF is able to transfer the documents either in straight-path mode or else the U-turn mode at the discretion of the user, demand has therefore arisen for ADF capable of operating in both the above-described modes.